Superlative form of fleshy; the most plump, muscular, or bodily-substantial of a group.
From 'flesh' plus '-y' (adjective) plus '-est' (superlative suffix). This is a three-step word formation: noun→adjective→superlative.
When you say 'fleshiest,' you're using one of the oldest comparison patterns in English—'-est' for superlatives goes back to Old English and Germanic roots, the same as 'fastest' and 'biggest'!
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